Aircraft Potable Water Use—
Adequate hydration is particularly important for comfortable air travel, especially aboard modern, very large, long range aircraft capable of flights of 20 or more hours duration. Typically, water is distributed to galleys, lavatories, and drinking water outlets of the aircraft to provide drinking water to passengers, to provide water for food and beverage preparation, and to provide water for personal hygiene (e.g., face and hand rinsing, teeth cleaning, etc.) during flights. Aircraft typically are crowded with thousands of passengers including babies, small children, handicapped people, possibly ill people, and others, from varied backgrounds, passing through a commercial passenger aircraft during a single week. Both passengers and crews contribute to microorganism populations aboard aircraft, and special precautions must be taken to minimize and avoid the possibility of bacteria, viruses, pathogenic cysts, and other microorganisms being transferred among passengers through the water distribution system. Further, water is supplied to aircraft from many locations and varies widely in taste and sanitary quality. In addition to point-of-use effective on-board drinking water microfilters/purifiers, a primary sanitation defense mechanism against bacteria and viruses is to maintain an adequate residual of chlorine, preferably free chlorine, within the water storage and distribution systems. Further, effective on-board point-of-use drinking water microfilters/purifiers reliably remove parasitic cysts (leading causes of water borne disease worldwide) such as Giradia and Crypto which are not controlled by chlorination.
Aircraft Water Distribution and Management—
Typically, a water distribution system on aircraft comprises a water storage tank supplying a centralized distribution line with various branches or legs extending from the central distribution line to locations throughout the aircraft. For example, water is distributed via the water distribution system to galleys, lavatories, and other locations as needed for food and beverage preparation, and for personal hygiene during flights. Galleys include many “service points” such as coffee makers, water boilers, and drinking water outlets. Similarly, lavatories often include drinking water outlets and may be used for face and hand rinsing, cleaning teeth and short term personal medication. There are many possible opportunities for aircraft drinking water systems/supplies to become contaminated with microorganisms even if hygienically safe when loaded aboard an aircraft.
Typically, water filter/purifier units, each comprising a housing pressure vessel and a filtration/purification cartridge, are installed in or near galleys and lavatories as part of the aircraft water distribution system to improve water quality for consumption and for food and beverage preparation. Purifiers (water filter/purifiers having a purification element) must be independently certified to meet the EPA Guide Standard Protocol for Microbiological Purifiers relative to bacteria, viruses and cysts. Structured Matrix™ purifiers, sold by General Ecology, Inc., also provide excellent filtration. Filters, such as General Ecology, Inc.'s Structured Matrix™ microfilters or simple, fine, or coarse carbon and/or sediment systems, may be sophisticated, but such filters cannot legally be referred to as microbiological purifiers before being verified that they meet the EPA Guide Standard Protocol for Microbiological Purifiers. Space in galley and lavatory compartments is expensive and severely limited. Accordingly, water filter/purifier units usually are installed in “out of the way”, often difficult to access locations often behind other more readily accessible equipment and bulkheads.
Sanitation Practices—
Possible microorganisms of concern are pathogenic bacteria, cysts and viruses. Chlorine resistant pathogenic cysts such as Crypto require special consideration and protective measures, such as providing point-of-use water filter/purifier units (e.g., water purifiers along the aircraft water distribution system to remove pathogenic cysts from the water moving through them). Such water filter/purifier units also remove bacteria, viruses, and other microorganisms from the water moving through them. Further, to overcome the challenges of virus and bacteria transmission via water systems and colonization within the aircraft potable water distribution systems, airlines often try to assure an adequate chlorine residual within the aircraft water supply. Even so, it is necessary to periodically “sanitize” the aircraft water distribution system, typically with a 2+ hours soak of high concentration (100 ppm) chlorine solutions. The sanitation process requires time and labor intensive removal of filtration/purification cartridges from the water filter/purifier units installed in galleys, fountains, and lavatories throughout the aircraft prior to the sanitation process. After removal of cartridges, pressure vessels must be reassembled to allow complete distribution of the sanitizing solution through the water distribution system and to prevent leakage of this highly corrosive and oxidizing sanitizing solution during the two hours sanitization soak.
Cartridge removal is required for at least two reasons: 1) because a high concentration of chlorine is detrimental to most filtration/purification cartridges, and 2) more importantly, because microorganisms might be sheltered in crevices and imperfections at sealing surface interfaces (ideal locations for biofilm formation) of the water filter/purifier units compromising effectiveness of the sanitizing process, thereby allowing recolonization of the distribution system. Even though sanitization is recognized as effective, typically because of the relatively high cost of the sanitizing process and the revenue lost due to the downtime of the aircraft during the sanitizing process, sanitization is performed infrequently—possibly every six months or at a convenient “A Check” or more extensive maintenance intervals when other maintenance is carried out.
After chlorine flushing and soaking for two hours, following current practices, the pressure vessels once again are opened and the same cartridges (or new replacement cartridges) are installed. Potable water is flushed throughout the aircraft water distribution system to thoroughly remove the extremely high concentration sanitizing solutions. Several hours may be required to sanitize an aircraft resulting in costs averaging upwards to hundreds of dollars per unit. More efficient, lower cost sanitization would allow more frequent sanitization and provide possibly higher quality potable water with better economy.
System Draining and Refilling—
Water must be drained from aircraft during periods of non-use (such as overnight) in cold climates. Proposed EPA regulations require much more frequent draining and filling of water storage tanks in an effort to improve aircraft drinking water quality and safety. Draining and filling water systems requires “vacuum breaks” at equipment locations to allow water to be properly released and “vents” to allow air to escape in order to assure proper functioning of filters, purifiers, and other equipment. Although the very latest filter/purifier units include automatic vacuum breaks and venting, most aircraft units require manual actuation often resulting in inadequate water draining and filling.
Also, under the proposed EPA regulations, it is likely that accessing and actuating manual vents and vacuum breaks, sometimes previously ignored, may become a significantly higher maintenance cost item due to difficult access to the water filter/purifier units and aircraft “out of service” revenue costs.
Microorganism Growth—
Even with periodic sanitization, bacteria may colonize various branches (legs) of water distribution systems. Bacteria multiply rapidly, sometimes doubling in number in approximately 16 minutes. Therefore, a small number of bacteria may quickly reach infectious concentrations in water intended to be consumed, especially downstream of improperly installed/serviced filters/purifiers employed to remove chlorine, foul tastes, and odors. Further, water filter/purifier units installed in semi-remote locations along the water distribution system often require longer than desired distribution lines to specific service points (e.g., locations where the water is discharged from the water distribution system). These distribution lines provide unnecessary opportunities for previously purified water to be recontaminated from inadvertent inoculation, short term bacteria multiplication or biofilm formation/shedding that may have taken place in such distribution lines downstream of the water filter/purifier units.